A liquid metal-based self-adaptive sulfur-gallium composite for long-cycling lithium-sulfur batteries.

Lithium-sulfur (Li-S) batteries have been regarded as a promising candidate for energy storage owing to their ultrahigh theoretical capacity and low cost. However, the commercial application of Li-S batteries has been plagued by the huge volume change of sulfur, the insulative nature of solid active materials (S and Li2S) and the polysulfide shuttle. Here, a uniform sulfur-gallium core-shell structure (S@Ga) with an ultrathin liquid gallium shell was prepared by harnessing the reaction between sulfur and gallium via a facile mixing process. In this S@Ga composite, the thin gallium shell not only exhibits the self-adaptive characteristic to perfectly adapt to the varying volume change of sulfur, restraining the polysulfide shuttle, but also acts as a conductive agent to enhance the electronic/ion transmission, improving the rate capacity of the S@Ga cathode. Therefore, the resultant S@Ga cathode exhibits a high capacity of 1295 mA h g-1 at 0.1C and a high cycling stability with a small decay of 0.043% per cycle for 1000 cycles at 1C.